In a metal fabrication machine center environment having, for example, turret punches and right angle shears, to load a workpiece onto a worktable for cutting or punching and remove the workpiece (or parts finished therefrom) from the worktable, a loader and an unloader are used. Such loader/unloader system is well known and is represented for example by the Finn-Power cantilever loading and unloading units. In a small shop environment in which metal forming machinery consists mainly of nibbling tools and/or punches, the installation of such separate loading/unloading units would be cost prohibitive.
Prior to the instant invention, to remove a finished portion from a large workpiece, a right angle shear is used to cut the finished portion from the workpiece as illustrated in FIG. 1. In brief, as shown in FIG. 1, to remove finished portions from a workpiece 2, clamps 4 which grip the workpiece 2 are moved so as to place workpiece 2 underneath a right angle shear (not shown) such that finished portions 6, 7, 8 etc. can be cut from workpiece 2. The finished portions are then separately removed. In a machine center, the removal of the finished portions is done by the unloader unit. In a small shop environment, the finished portions are removed manually.
A second method in which finished portions are removed from a workpiece is shown in FIG. 2 where it can be seen that a plurality of finished pieces 9, 10, 11 are nibbled from workpiece 2 such that they become "shaker" parts which remain connected to workpiece 2 by a plurality of small linking sections. Once all of the finished portions are nibbled, workpiece 2 is removed from the worktable and shaked, so that the nibbled finished pieces fall out. One disadvantage with the shaker approach is that a large portion of workpiece 2 is wasted due to the need to leave a sufficient large skeleton base for holding the shaker pieces before those pieces are dislodged from workpiece 2.
The two finished part removal methods illustrated in FIGS. 1 and 2 are acceptable so long as a manufacturer can afford a right angle shear and/or willing to accept a large amount of waste.
A prior art system by the Finn-Power Company for overcoming the disadvantages of the methods mentioned above comprises a system having a frame mounted to the operating frame of the turret, nibbling tool etc. Mounted underneath the frame along a longitudinal direction is a drive cylinder that has connected underneath thereto a movable suction cup that can be moved up and down, and along the direction of the air cylinder so that the suction cup can come down and suction the finished workpiece and remove it from the worktable. The problem with such prior art system is that oftentimes the suction cup will butt against the remaining portion of the workpiece. Since oftentimes the workpiece is quite thin, it is readily damaged. Yet another disadvantage of the prior art system is that it is quite slow and requires a setting for the movement of the suction cup that has to be carefully maintained. If not, the suction cup may end up missing the mark and not suction the finished workpiece.